Section 2.7.1.: “If the Linked Entity is a Circle or a group, then a new special-purpose Cross Link Role is automatically created instead, and resides within both the Linked Entity and the Target Circle, much like a Rep Link. In this case, the Cross Link Role has the same Purpose and Accountabilities as a Rep Link, but with the “Circle” referenced in the Rep Link Role description instead meaning the Linked Entity, and the “Super-Circle” instead meaning the Target Circle.”
So the Lead Link of a Target Circle can define metrics for the Linked Entity.
We have that in H1 Ecosystem Circle for instance: https://glassfrog.holacracy.org/circles/1506
As a Provider, we have a Cross Link from our company (iGi Partners is the Linked Entity) to H1 (Target Circle) and the Lead Link of this Circle (Olivier) defined metrics Cross Links need to report on their company's activity.
Hope that helps!